KR20200082565A - Negative electrode comprising active material having a core-shell structure for secondary battery, menufacturing method of thereof, and secondary battery comprising the same - Google Patents

Abstract

The present invention relates to an ultra battery to which an active material having a core-shell structure is applied. By preparing core-shell structured composite particles composed of carbon and lead under physical mixing and heat treatment conditions at low temperature without additional additives and applying the same to a negative electrode of ultra batteries, an ultra battery with higher discharge capacity and performance than prior art can be provided.

Description

Cathode containing an active material having a core-shell structure, a manufacturing method thereof, and a secondary battery comprising the same

The present invention relates to a negative electrode comprising an active material having a core-shell structure, a method of manufacturing the same, and a secondary battery including the same, and more particularly, to an ultra battery to which an active material having a core-shell structure is applied.

Ultra battery is a battery for hybrid vehicles, and is a battery made by combining lead-acid batteries and ultra-capacitors (or super capacitors) used in existing internal combustion engines. In the transitional stage before the commercialization of lithium or fuel cells in the hybrid vehicle market, nickel-hydrogen batteries mainly occupy most of them until now. The nickel-hydrogen battery has excellent energy performance and energy density, as well as excellent lifespan performance. However, it has the disadvantage of being very expensive in price. To compensate for this, ultra-batteries have been developed to demonstrate very suitable performance in hybrid vehicles by combining low-cost, high-density lead-acid batteries and ultra-capacitor with excellent output density. The ultra battery has low cost, improved output characteristics, and long life, and thus has many developments. However, the ultra battery technology has not been properly developed in Korea, and it is urgently needed to develop a localization technology as it is a technology that is highly likely to enter the mass storage market as well as to apply hybrid vehicles in the future. In particular, there was still a large amount of energy lost due to the sulfation reaction between the electrolyte and the electrode containing lead due to the charge and discharge for a long time, and as a result, the discharge capacity was not high enough.

Korean Patent Publication No. 10-2010-0041928 relates to an ultra battery in which an ultracapacitor negative electrode and a lead acid battery negative electrode used as a negative electrode are formed in a multilayer in the same size as an ultra battery positive electrode, and a material having a large surface area such as activated carbon as an electrode material. It is characterized in that an electric double layer is formed on the surface of the electrode material and the contact surface of the electrolyte by using as an active material of the electrode. However, there is no suggestion of a method capable of suppressing the sulfation reaction and interface resistance between the electrolyte and the electrode surface.

Korean Patent Publication No. 10-2010-0041928

An object of the present invention is to provide a negative electrode active material capable of reducing activation loss and ohmic loss compared to a conventional lead acid battery by suppressing sulfation at the negative electrode during discharge.

An object of the present invention is to provide an electrode for an ultra battery that can be driven at a higher voltage in a forward voltage operation range and a method for manufacturing the same.

The object of the present invention is not limited to the object mentioned above. The object of the present invention will be more apparent from the following description, and will be realized by means described in the claims and combinations thereof.

According to the present invention, an electrode plate containing lead; And an active material layer provided on the electrode plate and including composite particles having a core-shell structure, wherein the core of the composite particles contains lead, and the shell of the composite particles contains carbon. It provides a negative electrode of a secondary battery comprising a.

The lead may be a crystalline structure oxidized by heat treatment.

The carbon may be a heat-treated, oxidized porous amorphous structure.

The average pore size of the carbon may be 1 to 100 nm.

The specific surface area of the composite particles may be 1 to 5,000 m 2 /g.

The specific surface area of the composite particles may be 900 to 1,500 m 2 /g.

The pore volume of the composite particles may be 0.1 to 20 cm ³ /g.

The ratio of the crystalline structure in the composite particles may be 0.1 to 50%.

The weight ratio of lead (Pb) and carbon (C) constituting the active material layer may be 1:0.001 to 1:9.

According to the invention, the anode; Any one of the cathodes; And an electrolyte interposed between the positive electrode and the negative electrode.

According to the present invention, physically mixing lead and carbon to prepare a mixture;

Heat-treating the mixture to prepare an active material including composite particles having a core-shell structure; Preparing an electrode slurry by mixing the active material with a binder and a solvent; And forming a coating layer by applying the electrode slurry to an electrode plate containing lead; in the manufacturing step, the lead includes lead particles having a diameter of 0.1 to 50 μm, and the In the step of manufacturing an active material, the lead is included in the core of the composite particle, and the carbon provides a method for manufacturing a negative electrode of a secondary battery, characterized in that it is included in the shell of the composite particle.

In the step of preparing the mixture, the carbon may include carbon particles having an average diameter of 0.01 to 50 μm.

In the step of preparing the mixture, the content of lead may be 10 to 99 parts by weight and the content of carbon may be 1 to 90 parts by weight.

In the step of preparing the mixture, the mixture may be prepared by physically stirring at 20 to 30° C. for 10 minutes to 24 hours.

In the step of manufacturing the active material, the composite particles may be prepared by heat treatment at 100 to 380° C. for 1 to 24 hours.

In the step of preparing the electrode slurry, the content of the active material may be 2 to 94% by weight, the content of the binder may be 1 to 48% by weight, and the content of the solvent may be 5 to 95% by weight.

In the step of preparing the electrode slurry, the binder is Nafion, polyester (PET), polyphenyl oxide (PPO), polytetrafluoroethylene (PTFE), polyether ether ketone (PEEK), polyvinylidene fluoride (PVDF) ), polyphenylene sulfide (PPS), sodium carboxymethylcellulose (CMC), styrene-butadiene rubber (SBR), polyethylene glycol (PEG), and combinations thereof.

In the cathode manufacturing step, the thickness of the coated active material layer may be 1 to 100 μm.

According to the present invention, by providing an active material having a core-shell structure in which lead and carbon are adsorbed, the interface resistance between the core-shell active material coating layer in the lead electrode and the lead electrode is reduced, thereby improving the performance of a secondary battery having a lower resistance than a conventional ultra battery. Can be implemented.

According to the present invention, it is possible to realize a higher discharge capacity than an ultra battery coated with only conventional carbon.

According to the present invention, physical mixing and low-temperature heat treatment are possible without additional additives, thereby reducing the cost of manufacturing the active material.

The effects of the present invention are not limited to the effects mentioned above. It should be understood that the effects of the present invention include all effects that can be deduced from the following description.

Figure 1 shows the active material manufacturing process comprising the composite particles of the core-shell structure of the present invention.
Figure 2 shows a transmission electron micrograph of the active material prepared through Examples 1 to 3.
Figure 3 shows a transmission electron micrograph of the active material prepared through Examples 4 to 6.
Figure 4 shows the graph analyzed by the X- ray diffraction method of the active material prepared through Examples 1 to 3.
5 is a graph showing the active material prepared through Examples 4 to 6 analyzed by X-ray diffraction.
6 is a graph analyzing the discharge performance of the battery incorporating the active material of Example 2 and Example 5.

The above objects, other objects, features and advantages of the present invention will be readily understood through the following preferred embodiments related to the accompanying drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided to ensure that the disclosed contents are thorough and complete and that the spirit of the present invention is sufficiently conveyed to those skilled in the art.

In describing each drawing, similar reference numerals are used for similar components. In the accompanying drawings, the dimensions of the structures are shown to be enlarged than the actual for clarity of the present invention. Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from other components. For example, the first component may be referred to as a second component without departing from the scope of the present invention, and similarly, the second component may be referred to as a first component. Singular expressions include plural expressions unless the context clearly indicates otherwise.

In this specification, the terms "include" or "have" are intended to indicate the presence of features, numbers, steps, actions, components, parts or combinations thereof described in the specification, one or more other features. It should be understood that the existence or addition possibilities of fields or numbers, steps, actions, components, parts or combinations thereof are not excluded in advance. In addition, when a part such as a layer, film, region, plate, etc. is said to be "on" another part, this includes not only the case of being "just above" the other part but also another part in the middle. Conversely, when a portion of a layer, film, region, plate, or the like is said to be “under” another portion, this includes not only the case “underneath” another portion, but also another portion in the middle.

Unless otherwise specified, all numbers, values, and/or expressions expressing amounts of ingredients, reaction conditions, polymer compositions, and blends used herein are those numbers that occur in obtaining these values, among other things. As these are approximations that reflect the various uncertainties of the measurement, it should be understood that in all cases they are modified by the term "about". In addition, when numerical ranges are disclosed in this description, these ranges are continuous, and include all values from the minimum value in this range to the maximum value including the maximum value, unless otherwise indicated. Further, when such a range refers to an integer, all integers including the minimum value to the maximum value including the maximum value are included unless otherwise indicated.

In the present specification, when a range is described for a variable, it will be understood that the variable includes all values within the stated range including the described endpoints of the range. For example, a range of “5 to 10” includes values of 5, 6, 7, 8, 9, and 10, as well as any subrange of 6 to 10, 7 to 10, 6 to 9, 7 to 9, and the like. It will be understood to include, and include any value between integers pertinent to the stated range of ranges such as 5.5, 6.5, 7.5, 5.5 to 8.5 and 6.5 to 9, and the like. Also, for example, the range of “10% to 30%” is 10% to 15%, 12% to 10%, 11%, 12%, 13%, etc. and all integers including up to 30% It will be understood that it includes any subranges such as 18%, 20% to 30%, etc., and includes any value between valid integers within the scope of the stated range, such as 10.5%, 15.5%, 25.5%, and the like.

The present invention relates to a negative electrode comprising an active material having a core-shell structure, a method of manufacturing the same, and a secondary battery including the same, and will be described in detail by dividing it into a configuration of a secondary battery and a method of manufacturing a secondary battery.

Secondary battery composition

The present invention relates to an ultra-cell comprising lead dioxide (PbO ₂ ) at the anode, lead (Pb) at the cathode, and sulfuric acid (H ₂ SO ₄ ) as an electrolyte, specifically, an electrode plate including lead; And an active material layer comprising composite particles having a core-shell structure.

Each configuration will be described based on the above features.

The active material layer formed on the negative electrode of the present invention includes composite particles having a core-shell structure. The core of the composite particle includes lead (Pb), and the shell is characterized by containing carbon (C).

The composite particles are produced through heat treatment, wherein the lead contained in the core has a specifically crystalline structure form in an aggregated form through heat treatment, and the carbon contained in the shell maintains a porous amorphous structure form. to be.

The average pore size of the porous carbon is 1 to 100 nm. It is preferably 1 to 10 nm, more preferably 1.75 to 1.82 nm.

The composite particles have a specific surface area of 1 to 5,000 m 2 /g, preferably 900 to 1,500 m 2 /g. This is a result of agglomeration of lead contained in the composite particles through heat treatment.

The pore volume of the composite particles is 0.1 to 20 cm ³ /g. Preferably from 0.2 to 10cm ³ / g, more preferably from 0.2 to 0.9cm ³ / g.

The core-shell structured composite particles are characterized in that the carbon particles surround the lead particles of the core. Specifically, the core-shell structure increases the area of electrochemical reaction with the electrolyte to suppress sulfation at the electrode interface. In addition, due to the above-described structure, the interface resistance between the active material layer and the electrode plate is reduced, so that the resistance of the battery can be significantly lowered.

The active material layer of the present invention is characterized by including the composite particles having the core-shell structure, wherein the ratio of the core having a crystalline structure in the composite particles is 0.1 to 50%. It is preferably 1 to 50%, more preferably 10 to 50%. In addition, the weight ratio of lead and carbon contained in the active material layer is characterized in that 1:0.001 to 1:9. If the weight ratio is out of the range, the core-shell structure may not be properly formed, and as a result, there is a problem that the desired effect of the present invention is not produced.

The electrode plate constituting the negative electrode of the present invention includes lead (hereinafter, referred to as a negative electrode plate), characterized in that the active material layer is coated on the negative electrode plate.

The thickness of the active material layer coated on the negative electrode plate is 1 to 100 μm. At this time, when the thickness of the active material layer is less than 1 μm, it is difficult to control the thickness of the active material layer when manufacturing a negative electrode, and a sufficient effect of inhibiting sulfation by carbon-lead composite particles cannot be expected. There is a problem that it is not smooth and it is difficult to control the suppression of lead sulfate (PbSO ₄ ) production.

The electrode plate constituting the anode of the present invention includes lead oxide (PbO ₂ ).

The electrolyte of the present invention includes sulfuric acid (H ₂ SO ₄ ), wherein the specific gravity of the sulfuric acid may be 1 to 3.

In the ultra battery of the present invention, a separator is wrapped around a negative electrode, wherein the separator is formed to perform a role of preventing contact between the positive electrode plate and the negative electrode. The separator preferably has a thickness of 0.01 to 5 mm, and its type is not particularly limited as long as it can be applied to an electrode composed of lead and lead oxide and a sulfuric acid electrolyte. In the present invention, absorbent glass fibers were used.

The unit cell constituting the ultra battery of the present invention is in a form of wrapping a separator on a negative electrode containing an active material, laminating the positive electrode plate on both sides of the negative electrode, and then wrapping the separator again.

Secondary battery manufacturing method

The secondary battery manufacturing method of the present invention comprises the steps of physically mixing lead and carbon to prepare a mixture; Heat-treating the mixture to prepare an active material including composite particles having a core-shell structure; Preparing an electrode slurry by mixing the active material with a binder and a solvent; It characterized in that it comprises; coating the electrode slurry on the electrode plate containing lead (coating) to form a coating layer to prepare a cathode.

Each of the above steps will be described to describe the cathode manufacturing method of the present invention. However, some overlapping features already described in the configuration of the secondary battery will be omitted.

Mixture preparation steps

This step is to physically mix lead and carbon to prepare a mixture. The carbon may be obtained by activating one coal selected from the group consisting of anthracite coal, bituminous coal, bituminous coal, lignite and combinations thereof.

The mixing is carried out in a manner of physically stirring 10 to 99 parts by weight of lead and 0.1 to 90 parts by weight of carbon at a temperature of 20 to 30° C. for 10 minutes to 24 hours. At this time, if the weight of the lead is out of the above range, uniform mixing may be difficult, resulting in poor workability.

Active material manufacturing stage

This is a step of manufacturing the active material including the core-shell structured composite particles by heat-treating the mixture.

FIG. 1 briefly shows a process in which carbon (a) and lead (b) are mixed to form a mixture (c), and the mixture is heat-treated to produce core-shell composite particles (d). The core of the composite particle (d) of the core-shell structure prepared through the heat treatment includes lead (b), and the shell comprises carbon (a). At this time, the lead is a crystalline structure (Crystal structure), the carbon has a porous (Porous) amorphous structure (Amorphous structure).

The heat treatment is performed for 1 to 24 hours at 100 to 380°C through an electric furnace. At this time, if it is less than 100℃, lead and tanson may not be properly activated, so that the desired composite particles may not be formed. If it exceeds 380℃, the time for cooling the composite particles may increase due to over-melting of lead, resulting in poor process efficiency. Occurs.

The composite particles produced by the heat treatment may be subjected to a separate cooling step, which is performed by stopping the operation of the electric furnace for 1 to 24 hours at room temperature.

Electrode slurry manufacturing steps

This is a step of preparing an electrode slurry by mixing the active material with a binder and a solvent. The slurry was prepared by mixing the heat-treated and cooled active material with a binder and then introducing it into a solvent.

The content of the active material, the binder and the solvent is 2 to 94% by weight of the active material based on the electrode slurry, 1 to 48% by weight of the binder and 5 to 95% by weight of the solvent.

The binder is Nafion (Nafion), polyester (PET), polyphenyl oxide (PPO), polytetrafluoroethylene (PTFE), polyether ether ketone (PEEK), polyvinylidene fluoride (PVDF), polyphenyl One selected from the group consisting of rensulfide (PPS), sodium carboxymethylcellulose (CMS), styrene-butadiene rubber (SBR), polyethylene glycol (PEG), and combinations thereof can be used.

The solvent may be one selected from the group consisting of water, ethanol, isopropyl alcohol, methanol, sulfuric acid, and combinations thereof. At this time, the sulfuric acid is a component that must be added to the solvent of the present invention.

Cathode manufacturing steps

This is a step of forming an active material layer by applying the electrode slurry to an electrode plate containing lead to produce a negative electrode. Specifically, the prepared electrode slurry is applied on the negative electrode plate, and the solvent is removed through a drying process. At this time, the thickness of the active material layer formed by completely removing the solvent is 1 to 100 μm.

Hereinafter, the present invention will be described in more detail through specific examples. The following examples are only examples for helping the understanding of the present invention, and the scope of the present invention is not limited thereto.

Example 1

3 g of lead and 7 g of carbon were quantified, placed in a bottle, and stirred for 1 hour using a ball mill to obtain a lead and carbon mixture. The mixture was poured into a crucible and heat-treated in an electric furnace at 150° C. for 6 hours to obtain composite particles. After the heat treatment was completed, the mixture was cooled to room temperature for 12 hours to obtain an active material having a core-shell structure.

Examples 2 to 6 and Comparative Example 1

Example 2 to Example 6, Comparative Example 1 to obtain an active material by varying the heat treatment temperature and mixing content as shown in Table 1 below.

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Comparative Example 1 Pb content 30% 30% 30% 50% 50% 50% 0% Heat treatment temperature 150℃ 200℃ 250℃ 150℃ 200℃ 250℃ - Comparative Example 1 is an active material composed only of carbon particles, and was not subjected to heat treatment.

Experimental Example 1 (TEM analysis)

Experiments were conducted to confirm the structures of the active materials of Examples 1 to 6 of the present invention.

2 is an analysis of the active material prepared through Examples 1 to 3 using a transmission electron microscope (Transmission Electron Microscope, TEM). Referring to this, it can be confirmed that when the lead content is 30%, carbon particles are adsorbed on the surface of the lead, the lead is a core, and the carbon has a shell-like structure.

3 is an analysis of the active material prepared through Examples 4 to 6 using a transmission electron microscope. It can be seen that even when the lead content is 50%, carbon particles are adsorbed on the surface of the lead, the lead is a core, and the carbon has a shell-like structure. In addition, as the heat treatment temperature increases from 150°C to 250°C, it can be confirmed through FIGS. 2 and 3 that carbon is better adsorbed on the lead surface.

Experimental Example 2 (XRD analysis)

Experiments were conducted to confirm the crystallinity of the active materials of Examples 1 to 6 of the present invention.

4 and 5 is an analysis of the active material of Examples 1 to 6 by X-ray diffraction (XRD). 4 and 5, it was confirmed that as the amount of lead increased and the heat treatment temperature increased, the intensity of carbon (amorphous) 14 to 24° decreased, and the crystal peak of lead appeared sharper. can do. Through this, it can be seen that the amorphous region of carbon decreases as the crystallinity of lead increases.

Experimental Example 3 (BET analysis)

To confirm the specific surface area and pore size of the active materials prepared in Examples 1 to 6 and Comparative Example 1, BET (Brunauer Emmett Teller) analysis was performed, and the results are shown in Table 2 below.

BET Comparative Example 1 150℃ 200℃ 250℃ Example 1 Example 4 Example 2 Example 5 Example 3 Example 6 Specific surface area
(㎡/g) 1832 1212 838 1240 854 1225 848 Average pore size (nm) 1.84 1.78 1.79 1.79 1.81 1.80 1.80 Total pore volume
(Cm3/g) Pb 0% (0.8)> Pb 30% (0.5)> Pb 50% (0.3)

Referring to the results of Table 2, it can be seen that as the content of lead increases, the specific surface area decreases due to formation of agglomerated mass. In addition, it can be seen that as the temperature increases, the adsorption reaction of lead and carbon increases, and the mass of agglomeration deepens, but the pore size does not change significantly.

Experimental Example 4 (Evaluation of secondary battery discharge performance)

In order to analyze the discharge performance of the secondary battery into which the active materials of Examples 2 and 5 were introduced, secondary batteries were prepared from the active materials of Examples 2, 5, and Comparative Example 1 to analyze the discharge performance, and the results were analyzed. It is represented by a graph of.

For the experiment, the cells were charged with a constant current of 0.1 A until the shell voltage became 2.3 V, and then charged again with a constant current of 0.05 A for 4 hours, and then discharged with a constant current of 0.1 A until the shell voltage became 1.75.

Referring to FIG. 5, the secondary batteries of Examples 2 and 5 were found to be at a level corresponding to the secondary batteries of Comparative Example 1.

Specifically, since the active materials of Examples 2 and 5 suppressed sulfation and reduced the electrode interface resistance, the battery resistance was significantly lowered, so that the voltage at discharge was maintained at a level corresponding to Comparative Example 5. Able to know. In addition, the active material of the core-shell structure of the present invention can be confirmed that the initial discharge capacity corresponds to a battery in which only carbon is introduced as an active material coating layer due to the structure in which lead and carbon are adsorbed, and the discharge capacity increases as the content of lead increases. can confirm.

As described above, the battery incorporating the active material of the present invention can exhibit stable discharge voltage characteristics due to battery resistance at a level equivalent to that of a conventional lead acid battery, and thus can exhibit improved discharge capacity compared to a conventional ultra battery. Stable performance of a lead acid battery or an ultra battery containing an active material may be secured.

a: carbon
b: lead
c: mixture
d: composite particles

Claims (17)

An electrode plate containing lead; And
It is provided on the electrode plate, the core-shell (core-shell) active material layer containing the composite particles; includes,
The core of the composite particle contains lead,
The shell of the composite particle contains carbon,
The negative electrode of the secondary battery, characterized in that the specific surface area of the composite particles is 1 to 5,000 m 2 /g. According to claim 1,
The lead is a negative electrode of a secondary battery, characterized in that the crystalline structure oxidized by heat treatment. According to claim 1,
The carbon is a negative electrode of a secondary battery, characterized in that the amorphous structure of the porous oxidized by heat treatment. According to claim 1,
The anode of the secondary battery, characterized in that the average pore size of the carbon is 1 to 100㎚. According to claim 1,
The negative electrode of the secondary battery, characterized in that the specific surface area of the composite particles is 900 to 1,500 m 2 /g. According to claim 1,
Method for manufacturing a negative electrode of a secondary battery, characterized in that the pore volume of the composite particles is 0.1 to 20 cm ³ /g. According to claim 1,
The ratio of the crystalline structure in the composite particles is a negative electrode of a secondary battery, characterized in that 0.1 to 50%. According to claim 1,
The weight ratio of lead (Pb) and carbon (C) constituting the active material layer is 1:0.001 to 1:9 negative electrode of a secondary battery, characterized in that. anode;
The negative electrode of any one of claims 1 to 6; And
And an electrolyte provided between the positive electrode and the negative electrode. Preparing a mixture by physically mixing lead and carbon;
Heat-treating the mixture to prepare an active material including composite particles having a core-shell structure;
Preparing an electrode slurry by mixing the active material with a binder and a solvent; And
Including the electrode manufacturing step of applying the electrode slurry to an electrode plate containing lead to form a coating layer;
In the step of preparing the mixture, the lead contains lead particles having a diameter of 0.1 to 50 μm,
In the step of manufacturing the active material, the lead is included in the core of the composite particle, and the carbon is included in the shell of the composite particle. The method of claim 10,
In the manufacturing step of the mixture, the carbon is a cathode manufacturing method of a secondary battery, characterized in that it comprises carbon particles having an average diameter of 0.01 to 50㎛. The method of claim 10,
In the step of preparing the mixture, the lead content is 10 to 99 parts by weight and the carbon content is 0.1 to 90 parts by weight of the negative electrode manufacturing method of the secondary battery. The method of claim 10,
In the step of preparing the mixture, the mixture is physically stirred at 20 to 30° C. for 10 minutes to 24 hours to produce a negative electrode for a secondary battery. The method of claim 10,
In the step of manufacturing the active material, the composite particles are prepared by heat treatment at 100 to 380° C. for 1 to 24 hours, thereby producing a negative electrode for a secondary battery. The method of claim 10,
In the step of manufacturing the electrode slurry, the content of the active material is 2 to 94% by weight, the content of the binder is 1 to 48% by weight, and the content of the solvent is 5 to 95% by weight of the negative electrode manufacturing method of the secondary battery . The method of claim 10,
In the step of preparing the electrode slurry, the binder is Nafion, polyester (PET), polyphenyl oxide (PPO), polytetrafluoroethylene (PTFE), polyether ether ketone (PEEK), polyvinylidene fluoride (PVDF) ), polyphenylene sulfide (PPS), sodium carboxymethylcellulose (CMS), styrene-butadiene rubber (SBR), polyethylene glycol (PEG), and combinations thereof. Way. The method of claim 10,
The cathode active method of the secondary battery, characterized in that the thickness of the coated active material layer in the cathode manufacturing step is 1 to 100㎛.

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